Linux & X11 & IRQ Interrupts

Linux & X11 & IRQ Interrupts

[Justin Piszcz]

When I move the mouse under X11 I hear a buzzing sound in the computer,
first, I found it was the console speaker.

Yet, I still hear a very faint sound when I move the mouse cursor, this
is after I've disconnected the console speaker, no matter what the rate
of interrupts.

from itop:

INT                NAME          RATE             MAX
  0 [             timer]   101 Ints/s     (max:   101)
  1 [          keyboard]     1 Ints/s     (max:     1)
  5 [              eth0]     2 Ints/s     (max:     4)
 12 [        PS/2 Mouse]   276 Ints/s     (max:   276)

Other people have also reported this problem but there hasn't been an
apparent fix for it yet?

With the console speaker attached, it can be clearly heard, as well as
performing fast packet movements (nmap (with insane option)) or such you
can literally hear the packets.

When I am compiling an application or spending interrupts on disk
access (copying files/doing a find), moving the mouse/holding a key on
the keyboard does not make noise.

Does anyone know the source of this problem, and possibly a solution, or
something one can do to mute this annoying noise?

This noise does not occur in any version of MS windows, so I am curious
as to what the kernel? or x11? is doing to produce this noise?

Re: Linux & X11 & IRQ Interrupts

[David D. Hagood]

Justin Piszcz wrote:

> With the console speaker attached, it can be clearly heard, as well as
> performing fast packet movements (nmap (with insane option)) or such you
> can literally hear the packets.


What you are hearing is the noise in the computer's power supply. As the 
load on the power supply changes, the voltage changes by a few tens of 
millivolts, and that is the noise you are hearing.

This primary reason you don't hear this under Windows and you hear it 
under Linux is that Linux will shut the processor off when there is 
nothing to do, greatly reducing the load on the power supply. When 
something happens, like a mouse interrupt or a network interrupt, the 
CPU springs back to life, drawing a burst of power from the power supply 
and momentarily bringing the voltage down a bit. This cycling of the CPU 
happens in microseconds.

Windows, especially older versions of Windows, doesn't do this - when 
there is no work for the CPU, it spins in a busy loop looking for work. 
As a result, the load on the power supply never changes. Of course, your 
system will also run hotter and burn more power.

If this bothers you, you could try getting another power supply (one 
that is "stiffer" and less prone to voltage sag) or you could run a 
program like Seti@home or Distributed.Net and keep your CPU busy all the 
time.

Re: Linux & X11 & IRQ Interrupts

[Justin Piszcz]

Ahh...
Thanks for the information.

"David D. Hagood" wrote:

> Justin Piszcz wrote:
>
> > With the console speaker attached, it can be clearly heard, as well as
> > performing fast packet movements (nmap (with insane option)) or such you
> > can literally hear the packets.
>
> What you are hearing is the noise in the computer's power supply. As the
> load on the power supply changes, the voltage changes by a few tens of
> millivolts, and that is the noise you are hearing.
>
> This primary reason you don't hear this under Windows and you hear it
> under Linux is that Linux will shut the processor off when there is
> nothing to do, greatly reducing the load on the power supply. When
> something happens, like a mouse interrupt or a network interrupt, the
> CPU springs back to life, drawing a burst of power from the power supply
> and momentarily bringing the voltage down a bit. This cycling of the CPU
> happens in microseconds.
>
> Windows, especially older versions of Windows, doesn't do this - when
> there is no work for the CPU, it spins in a busy loop looking for work.
> As a result, the load on the power supply never changes. Of course, your
> system will also run hotter and burn more power.
>
> If this bothers you, you could try getting another power supply (one
> that is "stiffer" and less prone to voltage sag) or you could run a
> program like Seti@home or Distributed.Net and keep your CPU busy all the
> time.

Re: Linux & X11 & IRQ Interrupts

[Alan Cox]

> When I move the mouse under X11 I hear a buzzing sound in the computer,
> first, I found it was the console speaker.
> Yet, I still hear a very faint sound when I move the mouse cursor, this
> is after I've disconnected the console speaker, no matter what the rate
> of interrupts.
> Other people have also reported this problem but there hasn't been an
> apparent fix for it yet?

Well you should probably discuss that with your power supply vendor. Linux
makes strong efforts to get the CPU in powered down mode as much as it can


Alan

Re: Linux & X11 & IRQ Interrupts

[Grogan]

Affirmative... A while back, my PC always used to make strange sounds when the hlt instruction was engaged/disengaged. It was a whine that changed in pitch. This happened in any OS that used it.  (Linux, Windows NT/2000, Windows 98 with the Rain CPU cooler program etc.). I just figured that was normal for my PC, until one day my power supply fan died and I had to replace the power supply. That was the last time I heard it.

Grogan

On Mon, 6 May 2002 16:24:27 +0100 (BST)
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> Well you should probably discuss that with your power supply vendor. Linux
> makes strong efforts to get the CPU in powered down mode as much as it can
> 
> 
> Alan

Re: Linux & X11 & IRQ Interrupts

[Diego Calleja]

On Sun, 05 May 2002 20:59:41 -0400
Justin Piszcz <war@starband.net> escribió:

> When I move the mouse under X11 I hear a buzzing sound in the computer,
> first, I found it was the console speaker.
I have the same problem. I've heard this in windows 9X with some programs wich just do what linux does, to cool the cpu.

I've tried a program wich just does:
main(){
	do{
	}while(1);
}

with the highest priority. (nice --19 ./cpu_sound). CPU time is 100% used,
 but the noise _doesn't_ disappears.
I suspect it's just that I've a cheap power supply, and a Cyrix 6x86MX processor....


> 
> Yet, I still hear a very faint sound when I move the mouse cursor, this
> is after I've disconnected the console speaker, no matter what the rate
> of interrupts.
> 
> from itop:
> 
> INT                NAME          RATE             MAX
>   0 [             timer]   101 Ints/s     (max:   101)
>   1 [          keyboard]     1 Ints/s     (max:     1)
>   5 [              eth0]     2 Ints/s     (max:     4)
>  12 [        PS/2 Mouse]   276 Ints/s     (max:   276)
> 
> Other people have also reported this problem but there hasn't been an
> apparent fix for it yet?
> 
> With the console speaker attached, it can be clearly heard, as well as
> performing fast packet movements (nmap (with insane option)) or such you
> can literally hear the packets.
> 
> When I am compiling an application or spending interrupts on disk
> access (copying files/doing a find), moving the mouse/holding a key on
> the keyboard does not make noise.
> 
> Does anyone know the source of this problem, and possibly a solution, or
> something one can do to mute this annoying noise?
> 
> This noise does not occur in any version of MS windows, so I am curious
> as to what the kernel? or x11? is doing to produce this noise?
> 
> 
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Re: Linux & X11 & IRQ Interrupts

[Tomas Szepe]

> [Diego Calleja <DiegoCG@teleline.es>, May-06 2002, Mon, 18:28 +0200]
>
> but the noise _doesn't_ disappears. I suspect it's just that I've a cheap
> power supply, and a Cyrix 6x86MX processor....

No matter how cheap it was, you should definitely return it and request
to be given a new one: Never underestimate any symptoms of dying hardware.
Last Christmas a big vendor here in .cz sold thousands of faulty cheap
power supplies -- majority of those blew up *all* of the connected
peripherals in a single 1-second flash (after a couple weeks in regular
use).


Tomas

Re: Linux & X11 & IRQ Interrupts

[Diego Calleja]

On Mon, 6 May 2002 18:46:44 +0200
Tomas Szepe <szepe@pinerecords.com> escribió:
> No matter how cheap it was, you should definitely return it and request
> to be given a new one: Never underestimate any symptoms of dying hardware.
> Last Christmas a big vendor here in .cz sold thousands of faulty cheap
> power supplies -- majority of those blew up *all* of the connected
> peripherals in a single 1-second flash (after a couple weeks in regular
> use).

Oh, I think it's no a problem, it has been working for about....3-4 years.


> 
> 
> Tomas

Re: Linux & X11 & IRQ Interrupts

[Andrew Morton]

"David D. Hagood" wrote:
> ...
> If this bothers you, you could try getting another power supply (one
> that is "stiffer" and less prone to voltage sag) or you could run a
> program like Seti@home or Distributed.Net and keep your CPU busy all the
> time.

You can just add `idle=poll' to the kernel boot command line.
Then the CPU will not be halted, and there will be less
variation in the current.

-